1. Field of the Invention
This invention relates to retrofocus type large aperture wide angle objectives, and more particularly to a compact retrofocus type wide angle objective having a field angle of 52.degree. or thereabout with an F-number on the order of 2.8, and which is well corrected for aberrations.
2. Description of the Prior Art
In designing wide angle objectives for single lens relfex cameras, an increase in employment of compactness and large aperture ratio is occurring. Most of these wide angle objectives have been constructed in the form of an inverted telephoto type with the advantage that the back focal distance can be generally elongated. Since, on the other hand, the lens arrangement lacks symmetry, good correction of aberrations becomes difficult to perform. This difficulty tends to be intensified more and more as the field angle and the relative aperture are increased along with a further advance in the compactness of the entire system. It is known to provide a retrofocus type wide angle objective having an increased range with an increased relative aperture as, for example, in U.S. Pat. Nos. 3,748,021, 3,976,366, 3,981,563, 4,013,350, 4,061,421, and 4,188,092.